package cn.skyclass.hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

/**
 * Configures and provides access to Hibernate sessions, tied to the current
 * thread of execution. Follows the Thread Local Session pattern, see
 * {@link http://hibernate.org/42.html }.
 */
public class HibernateSessionFactory {

	/**
	 * Location of hibernate.cfg.xml file. Location should be on the classpath
	 * as Hibernate uses #resourceAsStream style lookup for its configuration
	 * file. The default classpath location of the hibernate config file is in
	 * the default package. Use #setConfigFile() to update the location of the
	 * configuration file for the current session.
	 */
	private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";

	private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();

	private static Configuration configuration = new Configuration();

	private static org.hibernate.SessionFactory sessionFactory;

	private static String configFile = CONFIG_FILE_LOCATION;

	private HibernateSessionFactory() {
	}

	/**
	 * Returns the ThreadLocal Session instance. Lazy initialize the
	 * <code>SessionFactory</code> if needed.
	 * 
	 * @return Session
	 * @throws HibernateException
	 */
	public static Session getSession() throws HibernateException {
		Session session = threadLocal.get();

		if (session == null || !session.isOpen()) {
			if (sessionFactory == null) {
				rebuildSessionFactory();
			}
			session = (sessionFactory != null) ? sessionFactory.openSession()
					: null;
			threadLocal.set(session);
		}

		return session;
	}

	/**
	 * Rebuild hibernate session factory
	 */
	public static void rebuildSessionFactory() {
		try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
	}

	/**
	 * Close the single hibernate session instance.
	 * 
	 * @throws HibernateException
	 */
	public static void closeSession() throws HibernateException {
		Session session = threadLocal.get();
		threadLocal.set(null);

		if (session != null) {
			session.close();
		}
	}

	/**
	 * return session factory
	 */
	public static org.hibernate.SessionFactory getSessionFactory() {
		return sessionFactory;
	}

	/**
	 * get the location of *.cfg.xml file
	 */
	public static String getConfigFile() {
		return HibernateSessionFactory.configFile;
	}

	/**
	 * return session factory session factory will be rebuilded in the next call
	 */
	public static void setConfigFile(String configFile) {
		// 如果将要更改的配置文件与当前的是同一个，则不更改，也就不必重新创建SessionFactory
		if (HibernateSessionFactory.configFile != configFile) {
			HibernateSessionFactory.configFile = configFile;
			sessionFactory = null;
		}
	}

	/**
	 * return hibernate configuration
	 */
	public static Configuration getConfiguration() {
		return configuration;
	}

}